Metabolic diseases are disorders that are caused due to the abnormal metabolisms in separate organs from the human body, and thus include generic types of diseases caused by impaired metabolisms resulting from the in vivo imbalance of saccharides, lipids, proteins, vitamins, minerals, moisture, etc. In particular, metabolic diseases caused due to the weakening of immunity and the lack of nutrition supply account for over 99% of the adult diseases. Most adult diseases are caused by the nutritional imbalance caused by inadequate food intake, the lack of exercise, etc.
Representative examples of the metabolic diseases include obesity, type 1 diabetes, type 2 diabetes, inadequate glucose tolerance, insulin resistance, hyperglycemia, hyperlipidemia, hypertriglyceridemia, hypercholesterolemia, dyslipidemia, syndrome X, etc. When the metabolic diseases cause fat accumulation in the body, insulin resistance occurs in which insulin that is a hormone which moves glucose from the blood into the liver and muscles is not normally produced or its functions decline, thereby causing an increase in blood glucose level and arteriosclerosis, which leads to the onset of the adult diseases.
As a representative example of the metabolic diseases, diabetes mellitus is a serious metabolic disease from which over one hundred million people suffer all over the world. There are over 12,000,000 diabetic patients in the U.S. and approximately 600,000 new patients have been diagnosed with the diabetes mellitus each year. All people who do not have the same cause of diabetes but have suffered from the diabetes mellitus commonly produce an excessive amount of glucose in the liver, and have no activity to move glucose into cells in which the glucose is used as a main fuel for the body. People who do not suffer from diabetes mellitus depend on insulin hormones produced in the pancreas so that the glucose moves from the blood into cells of the body. However, people suffering from the diabetes neither produce insulin nor efficiently use the insulin produced thereby, and thus cannot move the glucose into their cells. Therefore, residual glucose that does not move into the cells may accumulate in blood, causing a disease referred to as hyperglycemia and leading to serious health problems over time.
Also, diabetes mellitus is a metabolic or vascular syndrome, or a syndrome associated with neuropathic factors. In general, the metabolic syndrome characterized by hyperglycemia include changes in carbohydrate, fat and protein metabolisms caused since insulin secretion is lacking or significantly decreased, or insulin exists but has no effects. The vascular syndrome results from abnormal blood vessels which cause cardiovascular, retinal and renal complications. Dysfunction in the peripheral and autonomic nervous systems is also a part of the diabetic syndrome. In addition, diabetes has been reported to be associated with the onset of renal disease, ocular disease and neurologic problems. The renal disease (nephropathy) develops when a “filtration mechanism” in the kidney is damaged, and an excessive amount of proteins leak into the urine, resulting in impaired kidney function. Also, diabetes mellitus is a provoking cause of inducing damage to the posterior retina of an eye, and increases the risk of developing cataract and glaucoma.
More specifically, the diabetes mellitus may be classified into two clinical syndromes; type 1 and 2 diabetes mellitus. Type 1 diabetes mellitus known as insulin-dependent diabetes mellitus (IDDM) is caused by autoimmune destruction of pancreatic β-cells producing insulin, and requires regular administration of exogenous insulin. Type 2 diabetes mellitus known as non-insulin-dependent diabetes mellitus (NIDDM) appears to develop due to its loss of an ability to properly regulate a blood glucose level. The type 2 diabetes mellitus is characterized by a disorder developed in people suffering from the type 2 diabetes mellitus who are deficient in insulin secretion or exhibit insulin resistance, that is, hardly have insulin or cannot effectively take use of insulin.
In the prior art, the current therapy against diabetes mellitus encompasses insulin, insulin secretagogues, glucose-lowering effectors, peroxisome proliferator-activated receptor (PPAR) activators, etc. However, there are problems associated with currently available therapies, including hypoglycaemia, weight gain, a decreased responsiveness to treatment over time, gastrointestinal dysfunction, and edema.
Accordingly, research has been conducted in various fields to introduce a more effective new therapy into the market. One specific target is G protein-coupled receptor 119 (GPR-119).
GPR-119 is one of G-protein-coupled receptors (GPCRs) that are mainly expressed in pancreatic, small intestinal, rectal and adipose tissues. When a ligand or agonist binds to the receptor, the receptor is structurally changed, and coupled to G-protein to catalyze reactions of secondary messengers in cells or organs.
GPR-119 receptors and isoforms thereof are found in mammalian species including humans, rats, mice, hamsters, chimpanzees, rhesus monkeys, cattle, and dogs. In particular, it is known that the expression of GPR-119 in pancreatic β-cells indicates that the GPR-119 receptors exert an effect on the insulin secretion. The activation of GPR-119 stimulates a cyclic adenosine monophosphate (cAMP) single pathway in which the intracellular activity of cAMP as a secondary messenger is enhanced in these cells. The stimulation of cAMP is involved in a variety of cellular reactions, such as expression of enzymes or genes, etc., and the stimulation of cAMP in the β-cells is induced through the activation of GPR-119. Also, gastric inhibitory polypeptides (GIPs), glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and the like cause an insulin secretion action through the G-protein-coupled receptor in the β-cells. Incretins such as the GIP and GLP-1 are gut hormones that strongly stimulate the insulin secretion in a blood glucose level-dependent manner after meals.
GPR-119 activators are effective in improvements in β-cell functions and β-cell groups. The activation of GPR-119 stimulates the insulin secretion in vitro and in vivo (rodents) in a glucose-dependent manner. The finding of potent GPR-119 activators may reduce a level of plasma glucose to promote blood glucose control without the risk of developing hypoglycemia.
In recent years, it was shown that the GPR-119 activators efficiently reduce a blood glucose level in diabetic rodents without the risk of developing hypoglycemia. It was confirmed that the secretion of both insulin and incretin induced by the GPR-119 activators is dependent on the GPR-119 receptors in GPR-119-knockout animals. Also, it was shown that the GPR-119 activators induce weight loss in Sprague Dawley rats by reducing the food intake.
Non-patent document 1 discloses that the activation of GPR-119 induce cAMP to induce secretion of glucose-dependent glucagon-like peptide-1 (GLP-1) and insulin (T. Soga et al., Biochem. Biophy. Res. Commu. 326, (2005), 744-751). It was found that GLP-1 mediates its action through GLP-1R that is a certain G protein-coupled receptor (GPCR), regulates glucose homeostasis, stimulates glucose-dependent insulin secretion, and increases a mass of pancreatic β-cells. Also, it was found that GLP-1 slows down a gastric emptying rate and improves satiety.
However, the existing GLP-1 peptide activators have a negative effect on effectiveness due to deficiency in bioavailability when administered orally. Therefore, there is a demand for development of GPR-119 activators that exhibit excellent oral bioavailability and induce the secretion of GLP-1 into the blood as well.
As one example of the research results, it was proven that the GPR-119 activators disclosed in Patent Documents 1-2 and Non-patent Document 2 cause an acute decline in food intake after chronic administration, resulting in reduced body weight in rats. Also, Patent Document 3 discloses the therapeutic agents for treating metabolic diseases using trisubstituted pyrimidine derivatives with the growing interest in trisubstituted heteroaryl derivatives. Further, Patent Document 4 discloses the therapeutic agents for treating diabetes mellitus using aryl, heteroaryl or heterocyclyl derivatives, characterized in that the therapeutic agents activate IC-GPCR2 or GPR-119 as therapeutic agents for type 1 diabetes mellitus associated with insulin resistance. However, there are no known compounds having a cyclohexene backbone and use thereof for treating metabolic diseases.
Accordingly, the present inventors have conducted research on activators of GPR-119, and found that a cyclohexene derivative according to the present invention, or an optical isomer or pharmaceutically acceptable salt thereof activates G protein-coupled receptor 119 (GPR-119) to enhance the intracellular activity of cyclic adenosine monophosphate (cAMP), and induces the release of glucagon-like peptide-1 (GLP-1), which is a neuroendocrine protein, to simultaneously exhibit weight-loss and hypoglycemic effects, and thus is useful for pharmaceutical compositions for preventing or treating metabolic diseases such as obesity, type 1 diabetes, type 2 diabetes, inadequate glucose tolerance, insulin resistance, hyperglycemia, hyperlipidemia, hypertriglyceridemia, hypercholesterolemia, dyslipidemia and syndrome X. Therefore, the present invention has been completed based on these facts.